This invention relates to rotors for automotive vehicle disk brakes and, more particularly, to rotors having a double row of cooling vents.
It is known in the art relating to automotive vehicle disk brakes to provide vented rotors having a single ring of air passages or cooling vents separated by annularly spaced cooling vanes. The vanes act as impellers that force air through the passages by centrifugal action during rotation of the brake rotor when the vehicle is moving. The vanes also connect the two cheeks of the rotor together and so affect the stiffness of the rotor by their structural characteristics. The air passing through the passages cools the brake rotor and the associated brake pads and thereby extends the life of the pads and improves the braking action of the pads against the rotor. A vented brake rotor has greater surface area per unit of mass of the rotor than an unvented rotor and has higher cooling rates due to both increased air velocity and increased surface area.
Two fundamental variables that influence the performance of a vehicle brake rotor are the cooling rate and the heating rate. The higher the cooling rate and the lower the heating rate the lower the braking temperature of a given rotor. Typically, the total width of a brake rotor will be fixed for a given vehicle in advance during the design and development of the vehicle. Increasing the air gap along the rotor axis will increase the cooling rate, however if the air gap along the axis is increased the cheek thickness will have to be reduced which brings down the mass of the rotor. The cooling rate and heating rate are opposing variables for a fixed rotor total width so that increasing one will decrease the other and vice versa. It is a problem then to find the optimum point where both cooling and heating rates are acceptable and rotor performance and pad wear life are maximized. Various changes, such as increasing the number of vanes, modifying vane shape or enhancing brake rotor and pad materials can affect the performance of a disk but may also adversely affect its structural and noise properties. Accordingly, improvements in the performance of the current version of a vented brake rotor generally represent compromises between performance and other required characteristics.
The present invention provides an improved brake rotor which provides a double row of vents with cooling vanes connecting inboard and outboard cheeks of a rotor to a central support ring. Each of the rows or rings of vents provides separate cooling to the adjacent cheek of the brake rotor and separate inlets are provided for the two rows of vents from opposite sides of the central support ring.
The double-vented brake rotor of the invention improves rotor performance in several ways. First, the surface area for heat transmission to the cooling air is increased by the introduction of two cheek faces connected to the central support ring. Second, the air flow rate is increased due to bifurcation of the air passages. Third, the flowing air is brought closer to the heat sources, which are the outer cheek faces. The result is that cooling performance of the new brake rotor is substantially improved. The design is such that the brake rotor is tangentially and axially rigid because the cooling vanes are relatively short and support the cheeks without substantial deflection, which leads to reduced noise propensity.
These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings.